It is well known that a moist environment helps the wound healing process by facilitating the interaction between cells and cell proliferation. Chemically modified cellulose, either by carboxymethylation or carboxyethylation, can enhance the properties of cellulose fibres such as the absorbency and gelling ability. Such a material can absorb as much as 15 times of liquid of its own weight. The chemically modified cellulose fibres can form gels on absorption of aqueous solutions to retain the moisture within the material, providing an ideal environment for wound healing and debridement. Furthermore, the gelled dressing can protect the wound by forming a semi-occlusive environment for the wound from the invasion of harmful substances. The chemically modified cellulose also expands on absorbing the fluid, creating a light pressure to the wound bed which would help blood circulation, supply of nutrients and removal the wastes.
Seacell fibres are essentially cellulose/alginate co-spun fibres, made by co-spinning cellulose and alginate through a solvent spun process. The majority of the fibres are cellulose but have alginate particles embedded in the fibres structure. It is a novel re-generated fibre, combining the benefits of both cellulose and alginate. The fibres can provide protein, amino, fat, cellulose and affluent mineral substance making it ideal for medical applications. Essentially, the Seacell fibres are made from the manufacturing procedure of Lyocell fibres, where the finely grinded alginate powder is blended into the cellulose spinning solution. In particular the alginate powder is grinded to fine particles of less than 9 μm, and then transferred to the cellulose NMMO solution. Alternatively, the alginate powder can be introduced into the spinning solution before cellulose dissolution, with a spinning solution composed of cellulose, alginate, NMMO and water. The solution is then extruded into fibres through a wet spinning process. The seacell shares the similar properties with that of the Lyocell fibres, such as tensile strength, processability etc. Through electron microscopy, it can be seen that seacell fibres have a porous structure, with some horizontal orientation and low crystallization. It has been found that the properties of the alginate component in the finished fibres are maintained, allowing some ingredients of the alginate to be released through the porous structure of the fibres in a moist environment.
Compared with Lyocel fibres, the seacell fibres have the added alginate component which binds metal ions. Additionally, alginate particles contain some minerals which help skin regeneration. It also contains some antibacterial ingredients providing some protection to the skin.
CN101967698A describes the manufacturing method of alginate/cellulose co-spun fibres, which includes the following steps: (1) the cellulose pulp is placed into NaOH solution to get alkalized cellulose; (2) sodium alginate is introduced into alkalized cellulose, with a percentage of up to 1˜5% by weight; (3) CS2 is introduced into the above mixtures to start the reaction, and then dissolved by deionized water to attain cellulose/alginate xanthate viscose solution; (4) the spinning solution is made by filtration and deaeration of the cellulose/alginate xanthate viscose solution; (5) the said spinning solution is extruded to attain cellulose/alginate con-spun fibres; (6) after stretching and other further processing the cellulose/alginate co-spun fibres are made.
CN 101613893A describes the manufacturing method of bacterial cellulose/alginate co-spun fibres. The sodium alginate powder is placed into the bacterial cellulose solution with ultrasonic dispersion. The solution is then extruded through a wet spinning process to make the bacterial cellulose/alginate co-spun fibres. The fibres contain 5-20% by weight of sodium alginate and 80-95% of bacterial cellulose. The manufacturing method also includes dissolving bacterial cellulose into an imidazole chloride salt ionic solution at a concentration of 5˜10% by weight; followed by adding some fine sodium alginate powder into the above solution. After dispersion and deaeration, the said solution is extruded into a coagulant bath, dried and stretched to obtain the bacterial cellulose/alginate co-spun fibres.
CN101168869A describes a soy protein/alginate/cellulose fibre, as well as its manufacturing method. The spinning solution consists of soy protein, alginate and a high viscosity cellulose solution. The protein/alginate/cellulose co-spun fibres are obtained after multi-step coagulation process. The finished fibres contain 15-60% by weight of soy protein, 3-8% by weight of alginate and 32-82% of cellulose.
However, the above technology has obvious weakness, such as the particle size of alginate powder being too big, the dispersion of alginate powder not being very uniform and the independent relationship between the each component. Moreover, the finished fibre does not have sufficient absorbency and gelling ability which makes the fibre less ideal for being materials for wound dressings.